Prior art includes the following patents:
U.S. Pat. No. 2,737,709, issued to W. H. Lovelace on Mar. 13, 1956, discloses an apparatus for handling articles such as automobile radiators. A guide motor supplies rotational energy via a driven sprocket to an externally threaded shaft. Mounted on the shaft is a carriage which threadedly engages the shaft so that the carriage may move along a vertical guide column located next to the threaded shaft. The carriage contains a work table with a C-clamp attached for holding the work piece. The threaded shaft extends through the cariage and the carriage traverses the fixed length of the drive screw.
U.S. Pat. No. 3,987,681, issued to Keithley et al on Oct. 26, 1976, discloses a power driven clamping device mounted on the bottom bolster of a press. An air motor is attached to a geat unit which selectively rotates an elongated drive sleeve in opposite directions. The bottom portion of a clamping rod is threadably engaged to the interior threads of the drive sleeve so that the clamping rod may move linearly and clamp an adaptor plate in relation to the bolster. The clamping rod has a longitudinal slot formed in its exterior surface which engages a guide pin in the housing of the clamping device to allow the rod to move in a linear path. The clamping rod has an offset head at its top end which clamps the adaptor plate against the bolster. The Keithley device applies force to clamped adaptor which is inherently non co-linear with axis of travel of clamping rod along the sleeve.
U.S. Pat. No. 2,663,929, issued to L. M. Carpenter on Dec. 29, 1953, discloses a radiator bench having a base with an elevator drive screw and guide rails adjacent to the screw. A motor drives a housing along the screw while the weight of the housing is supported by the guide rails and an elevator platform mounted on the housing. The elevator drive screw extends through a housing and the housing traverses the fixed length of the drive screw.
U.S. Pat. No. 2,481,477, issued to W. E. Peery on Sept. 6, 1949, discloses a typical screw and nut actuator used to operating movable parts. An electric motor and gear system drive a rotating nut, causing it to rotate about a lead screw thereby affecting movement along the screw in a direction depending upon the direction of motor rotation. Peery discloses a screw and nut arrangement in combination with other elements to actuate a bed.
U.S. Pat. No. 4,024,959, issued to H. Gruner on May 24, 1977, discloses a handling system incorporating hydraulic and electric power systems in which the position of a gripper is controlled by four electric motors, two of which rotate threaded spindles so that a cross-head member containing threaded bores can be directed along two perpendicular axes. The gripper comprises a number of jaws controlled by hydraulic pistons. Two jaws are caused to approach one another by means of pressure supplied through connecting lines so that their corresponding pistons simultaneously move in opposite directions. The threaded spindle extends through a threaded base in the crosshead carrying an arm and is attached to the arm via a spindle bearing. Rotation of the spindle extends the arm (which also extends through the crosshead) along its axis.
U.S. Pat. No. 4,184,799, issued to M. Arndt on Jan. 22, 1980, discloses an arrangement which contains a gripping mechanism comprising slidably mounted gripper arm pairs on parallel rods and rotatable gripper plates. Outward movement of the gripper arms is carried out by means of a "hydraulic-respectively pneumatic-cylinder unit" mounted between the pairs of gripper arms. Clamping motion is carried out by a spring, also mounted between the gripper arm pairs. Action of gripper arms toward and away from each other to effect clamping action is accomplished by pneumatic-hydraulic and spring action disposed between and interconnecting the gripper jaws.
U.S. Pat. No. 4,014,443, issued to A. Asari et al on Mar. 29, 1977, discloses a device for delivering articles containing a moving clamp having jaws which are actuated by a linear drive source. The clamping movement is controlled by the simultaneous rotation of two running rods in opposite directions so that the attached jaws can open or close depending on the direction of the linear actuator. The rotation of the running rods may be controlled by such means as a rack-and-pinion mechanism, a slide-rod mechanism, a gear meachanism, or a cylindrical cam mechanism. In all cases the movement of the clamping jaws disclosed in the Asari et al patent is rotational.